Mosaic Disorders of the PI3K/PTEN/AKT/TSC/mTORC1 Signaling Pathway

Genetic basis and imaging findings of neurofibromatosis 1 and other somatic overgrowth disorders

Somatic overgrowth disorders comprise a wide range of rare conditions that present with focal enlargement of one or more tissue types. The PI3K-AKT-mTOR pathway is a signalling pathway that induces angiogenesis and cell proliferation, and is one of the most commonly overactivated signalling pathways in cancer. The PI3K-AKT-mTOR pathway can be up-regulated by genetic variants that code for proteins in this pathway, or down-regulated by proteins that inhibit the pathway. Mosaic genetic variations can result in cells that proliferate excessively in specific anatomical locations. The PIK3CA-related overgrowth spectrum (PROS) disorders include CLOVES syndrome, macrodystrophia lipomatosa, and Klippel-Trenaunay syndrome among many. The neurofibromatosis type 1 (NF1) gene encodes neurofibromin which down-regulates the PI3K-AKT-mTOR pathway. Thousands of pathological variants in the NF1 gene have been described which can result in lower-than-normal levels of neurofibromin and therefore up-regulation of the PI3K-AKT-mTOR pathway promoting cellular overgrowth. Somatic overgrowth is a rare presentation in NF1 with a wide range of clinical and radiological presentations. Hypertrophy of all ectodermal and mesodermal elements has been described in NF1 including bone, muscle, fat, nerve, lymphatics, arteries and veins, and skin. The shared signalling pathway for cellular overgrowth means that these radiological appearances can overlap with other conditions in the PIK3CA-related overgrowth spectrum. The aim of this review is to describe the genetic basis for the radiological features of NF1 and in particular compare the appearances of the somatic overgrowth disorders in NF1 with other conditions in the PIK3CA-related overgrowth spectrum.

Phosphoinositide Metabolism: Biochemistry, Physiology and Genetic Disorders

Phosphatidylinositol, a glycerophospholipid with a myo-inositol head group, can form seven different phosphoinositides (PItds) by phosphorylation at inositol carbons 3, 4 and/or 5. Over 50 kinases and phosphatases participate in PItd metabolism, creating an interconnected PItd network that allows for precise temporal and spatial regulation of PItd levels. We review paradigms of PItd action, including (1) the establishment of subcellular organelle identity by the acquisition of specific PItd signatures, permitting regulation of key processes of cell biology including trafficking (exocytosis, clathrin-dependent and -independent endocytosis, formation and function of membrane contact sites, cytoskeletal remodeling), (2) signaling through phospholipase C cleavage of phosphatidylinositol 4,5-bisphosphate to inositol 1,4,5-trisphosphate and DAG, and (3) roles of PItds in molecular transport at membrane contact sites. To date, variants in 34 genes of PItd metabolism account for at least 41 distinguishable monogenic conditions. Clinical presentations of these disorders produce a broad and often multisystemic spectrum of effects. The nervous system is often involved, and muscular, immunological, skeletal, renal, ophthalmologic and dermatologic features occur in several conditions. Some syndromes involving PItd metabolism can be distinguished clinically, but most diagnoses currently result from broad molecular diagnostic testing performed for the patient's presenting clinical complaint. Genetic disorders of PItd metabolism are a broad, expanding and challenging category of inborn errors. Challenges include improved documentation of the clinical spectra, development of broad biochemical diagnostic methods for these conditions and better understanding of the PItd networks in different cells and subcellular compartments necessary for the development of disease-specific therapies.

Targeted therapy of cancer stem cells: inhibition of mTOR in pre-clinical and clinical research

Cancer stem cells (CSCs) are a type of stem cell that possesses not only the intrinsic abilities of stem cells but also the properties of cancer cells. Therefore, CSCs are known to have self-renewal and outstanding proliferation capacity, along with the potential to differentiate into specific types of tumor cells. Cancers typically originate from CSCs, making them a significant target for tumor treatment. Among the related cascades of the CSCs, mammalian target of rapamycin (mTOR) pathway is regarded as one of the most important signaling pathways because of its association with significant upstream signaling: phosphatidylinositol 3‑kinase/protein kinase B (PI3K/AKT) pathway and mitogen‑activated protein kinase (MAPK) cascade, which influence various activities of stem cells, including CSCs. Recent studies have shown that the mTOR pathway not only affects generation of CSCs but also the maintenance of their pluripotency. Furthermore, the maintenance of pluripotency or differentiation into specific types of cancer cells depends on the regulation of the mTOR signal in CSCs. Consequently, the clinical potential and importance of mTOR in effective cancer therapy are increasing. In this review, we demonstrate the association between the mTOR pathway and cancer, including CSCs. Additionally, we discuss a new concept for anti-cancer drug development aimed at overcoming existing drawbacks, such as drug resistance, by targeting CSCs through mTOR inhibition.

Do metabolic deficits contribute to sleep disruption in monogenic intellectual disability syndromes?

Intellectual disability is defined as limitations in cognitive and adaptive behavior that often arise during development. Disordered sleep is common in intellectual disability and, given the importance of sleep for cognitive function, it may contribute to other behavioral phenotypes. Animal models of intellectual disability, in particular of monogenic intellectual disability syndromes (MIDS), recapitulate many disease phenotypes and have been invaluable for linking some of these phenotypes to specific molecular pathways. An emerging feature of MIDS, in both animal models and humans, is the prevalence of metabolic abnormalities, which could be relevant for behavior. Focusing on specific MIDS that have been molecularly characterized, we review sleep, circadian, and metabolic phenotypes in animal models and humans and propose that altered metabolic state contributes to the abnormal sleep/circadian phenotypes in MIDS.

Reverse repurposing: Potential utility of cancer drugs in nonmalignant illnesses

Growth and immune process dysregulation can result in both cancer and nonmalignant disease (hereditary or acquired, with and without predisposition to malignancy). Moreover, perhaps unexpectedly, many nonmalignant illnesses harbor genomic alterations indistinguishable from druggable oncogenic drivers. Therefore, targeted compounds used successfully to treat cancer may have therapeutic potential for nonmalignant conditions harboring the same target. MEK, PI3K/AKT/mTOR, fibroblast growth factor receptor (FGFR), and NRG1/ERBB pathway genes have all been implicated in both cancer and noncancerous conditions, and several cognate antagonists, as well as Bruton's tyrosine kinase inhibitors, JAK inhibitors, and CD20-directed antibodies, have established or theoretical therapeutic potential to bridge cancer and benign diseases. Intriguingly, pharmacologically tractable cancer drivers characterize a wide spectrum of disorders without malignant potential, including but not limited to Alzheimer's disease and a variety of other neurodegenerative conditions, rheumatoid arthritis, achondroplastic dwarfism, and endometriosis. Expanded repositioning of oncology agents in order to benefit benign but serious medical illnesses is warranted.

MicroRNAs targeted mTOR as therapeutic agents to improve radiotherapy outcome

MicroRNAs (miRNAs) are small RNA molecules that regulate genes and are involved in various biological processes, including cancer development. Researchers have been exploring the potential of miRNAs as therapeutic agents in cancer treatment. Specifically, targeting the mammalian target of the rapamycin (mTOR) pathway with miRNAs has shown promise in improving the effectiveness of radiotherapy (RT), a common cancer treatment. This review provides an overview of the current understanding of miRNAs targeting mTOR as therapeutic agents to enhance RT outcomes in cancer patients. It emphasizes the importance of understanding the specific miRNAs that target mTOR and their impact on radiosensitivity for personalized cancer treatment approaches. The review also discusses the role of mTOR in cell homeostasis, cell proliferation, and immune response, as well as its association with oncogenesis. It highlights the different ways in which miRNAs can potentially affect the mTOR pathway and their implications in immune-related diseases. Preclinical findings suggest that combining mTOR modulators with RT can inhibit tumor growth through anti-angiogenic and anti-vascular effects, but further research and clinical trials are needed to validate the efficacy and safety of using miRNAs targeting mTOR as therapeutic agents in combination with RT. Overall, this review provides a comprehensive understanding of the potential of miRNAs targeting mTOR to enhance RT efficacy in cancer treatment and emphasizes the need for further research to translate these findings into improved clinical outcomes.

Extracranial Vascular Anomalies Driven by RAS/MAPK Variants: Spectrum and Genotype-Phenotype Correlations

BACKGROUND

We aimed to correlate alterations in the rat sarcoma virus (RAS)/mitogen-activated protein kinase pathway in vascular anomalies to the clinical phenotype for improved patient and treatment stratification.

METHODS AND RESULTS

This retrospective multicenter cohort study included 29 patients with extracranial vascular anomalies containing mosaic pathogenic variants (PVs) in genes of the RAS/mitogen-activated protein kinase pathway. Tissue samples were collected during invasive treatment or clinically indicated biopsies. PVs were detected by the targeted sequencing of panels of genes known to be associated with vascular anomalies, performed using DNA from affected tissue. Subgroup analyses were performed according to the affected genes with regard to phenotypic characteristics in a descriptive manner. Twenty-five vascular malformations, 3 vascular tumors, and 1 patient with both a vascular malformation and vascular tumor presented the following distribution of PVs in genes: Kirsten rat sarcoma viral oncogene (n=10), neuroblastoma ras viral oncogene homolog (n=1), Harvey rat sarcoma viral oncogene homolog (n=5), V-Raf murine sarcoma viral oncogene homolog B (n=8), and mitogen-activated protein kinase kinase 1 (n=5). Patients with RAS PVs had advanced disease stages according to the Schobinger classification (stage 3-4: RAS, 9/13 versus non-RAS, 3/11) and more frequent progression after treatment (RAS, 10/13 versus non-RAS, 2/11). Lesions with Kirsten rat sarcoma viral oncogene PVs infiltrated more tissue layers compared with the other PVs including other RAS PVs (multiple tissue layers: Kirsten rat sarcoma viral oncogene, 8/10 versus other PVs, 6/19).

CONCLUSIONS

This comparison of patients with various PVs in genes of the RAS/MAPK pathway provides potential associations with certain morphological and clinical phenotypes. RAS variants were associated with more aggressive phenotypes, generating preliminary data and hypothesis for future larger studies.

The Genetics of Tuberous Sclerosis Complex and Related mTORopathies: Current Understanding and Future Directions

The mechanistic target of rapamycin (mTOR) pathway serves as a master regulator of cell growth, proliferation, and survival. Upregulation of the mTOR pathway has been shown to cause malformations of cortical development, medically refractory epilepsies, and neurodevelopmental disorders, collectively described as mTORopathies. Tuberous sclerosis complex (TSC) serves as the prototypical mTORopathy. Characterized by the development of benign tumors in multiple organs, pathogenic variants in TSC1 or TSC2 disrupt the TSC protein complex, a negative regulator of the mTOR pathway. Variants in critical domains of the TSC complex, especially in the catalytic TSC2 subunit, correlate with increased disease severity. Variants in less crucial exons and non-coding regions, as well as those undetectable with conventional testing, may lead to milder phenotypes. Despite the assumption of complete penetrance, expressivity varies within families, and certain variants delay disease onset with milder neurological effects. Understanding these genotype-phenotype correlations is crucial for effective clinical management. Notably, 15% of patients have no mutation identified by conventional genetic testing, with the majority of cases postulated to be caused by somatic TSC1/TSC2 variants which present complex diagnostic challenges. Advancements in genetic testing, prenatal screening, and precision medicine hold promise for changing the diagnostic and treatment paradigm for TSC and related mTORopathies. Herein, we explore the genetic and molecular mechanisms of TSC and other mTORopathies, emphasizing contemporary genetic methods in understanding and diagnosing the condition.

The allosteric mechanism of mTOR activation can inform bitopic inhibitor optimization

mTOR serine/threonine kinase is a cornerstone in the PI3K/AKT/mTOR pathway. Yet, the detailed mechanism of activation of its catalytic core is still unresolved, likely due to mTOR complexes' complexity. Its dysregulation was implicated in cancer and neurodevelopmental disorders. Using extensive molecular dynamics (MD) simulations and compiled published experimental data, we determine exactly how mTOR's inherent motifs can control the conformational changes in the kinase domain, thus kinase activity. We also chronicle the critical regulation by the unstructured negative regulator domain (NRD). When positioned inside the catalytic cleft (NRD IN state), mTOR tends to adopt a deep and closed catalytic cleft. This is primarily due to the direct interaction with the FKBP-rapamycin binding (FRB) domain which restricts it, preventing substrate access. Conversely, when outside the catalytic cleft (NRD OUT state), mTOR favors an open conformation, exposing the substrate-binding site on the FRB domain. We further show how an oncogenic mutation (L2427R) promotes shifting the mTOR ensemble toward the catalysis-favored state. Collectively, we extend mTOR's "active-site restriction" mechanism and clarify mutation action. In particular, our mechanism suggests that RMC-5552 (RMC-6272) bitopic inhibitors may benefit from adjustment of the (PEG8) linker length when targeting certain mTOR variants. In the cryo-EM mTOR/RMC-5552 structure, the distance between the allosteric and orthosteric inhibitors is ∼22.7 Å. With a closed catalytic cleft, this linker bridges the sites. However, in our activation mechanism, in the open cleft it expands to ∼24.7 Å, offering what we believe to be the first direct example of how discovering an activation mechanism can potentially increase the affinity of inhibitors targeting mutants.

Morphological and radiological features of congenital muscular hypertrophy of the upper limb: experience from a tertiary institution

Congenital muscular hypertrophy is a rare overgrowth disorder in the phosphatidylinositol-3-kinase related spectrum. In the past 3 years, ten patients with 11 limbs involved were treated in our centre. The aim of the study was to describe the clinical and radiological deformities of these patients. We documented the characteristic clinical morphological changes, such as hypertrophy, loss of wrist flexion, thumb hyperabduction, finger deviation and skin crease changes in the palm. Radiologically, the mean first metacarpal radial deviation angle of the affected side measured 55° (range 34 to 67) compared to the normal contralateral side 42° (range 32 to 53). The mean intermetacarpal space ratio was 1.2 (range 1.1 to 1.4) and the mean palm width ratio was 1.2 (range 1.1 to 1.3). In this study, we were able to further characterize the radiological and morphological changes of congenital muscular hypertrophy of upper limbs, which would be helpful for establishing the diagnosis and monitor treatment of this rare condition.Level of evidence: IV.

The Important Role of Protein Kinases in the p53 Sestrin Signaling Pathway

p53, a crucial tumor suppressor and transcription factor, plays a central role in the maintenance of genomic stability and the orchestration of cellular responses such as apoptosis, cell cycle arrest, and DNA repair in the face of various stresses. Sestrins, a group of evolutionarily conserved proteins, serve as pivotal mediators connecting p53 to kinase-regulated anti-stress responses, with Sestrin 2 being the most extensively studied member of this protein family. These responses involve the downregulation of cell proliferation, adaptation to shifts in nutrient availability, enhancement of antioxidant defenses, promotion of autophagy/mitophagy, and the clearing of misfolded proteins. Inhibition of the mTORC1 complex by Sestrins reduces cellular proliferation, while Sestrin-dependent activation of AMP-activated kinase (AMPK) and mTORC2 supports metabolic adaptation. Furthermore, Sestrin-induced AMPK and Unc-51-like protein kinase 1 (ULK1) activation regulates autophagy/mitophagy, facilitating the removal of damaged organelles. Moreover, AMPK and ULK1 are involved in adaptation to changing metabolic conditions. ULK1 stabilizes nuclear factor erythroid 2-related factor 2 (Nrf2), thereby activating antioxidative defenses. An understanding of the intricate network involving p53, Sestrins, and kinases holds significant potential for targeted therapeutic interventions, particularly in pathologies like cancer, where the regulatory pathways governed by p53 are often disrupted.

A Mosaic PIK3CA Mutation in a Moroccan Female: Exploring the Diagnostic Challenges of PIK3CA-Related Overgrowth Spectrum

The PIK3CA-related overgrowth spectrum (PROS) encompasses a group of rare disorders characterized by the overgrowth of various body parts, driven by mutations in the PIK3CA gene. This study presents a case of a Moroccan female patient with PROS, demonstrating a phenotype associated with genetic mosaicism in the PIK3CA gene. A multidisciplinary approach, involving clinical examination, radiological assessment, and genetic and bioinformatic analyses, was employed for diagnosis and management. Next-generation sequencing and Sanger sequencing identified a rare variant, c.353G>A, in exon 3 of the PIK3CA gene, not detected in leukocyte DNA but confirmed in tissue biopsy samples. The comprehensive analysis of this case furthers our understanding of PROS and highlights the importance of a multidisciplinary approach to the diagnosis and management of this rare disorder.

Pten associates with important gene regulatory network to fine-tune Müller glia-mediated zebrafish retina regeneration

Unlike mammals, zebrafish possess a remarkable ability to regenerate damaged retina after an acute injury. Retina regeneration in zebrafish involves the induction of Müller glia-derived progenitor cells (MGPCs) exhibiting stem cell-like characteristics, which are capable of restoring all retinal cell-types. The induction of MGPC through Müller glia-reprograming involves several cellular, genetic and biochemical events soon after a retinal injury. Despite the knowledge on the importance of Phosphatase and tensin homolog (Pten), which is a dual-specificity phosphatase and tumor suppressor in the maintaining of cellular homeostasis, its importance during retina regeneration remains unknown. Here, we explored the importance of Pten during zebrafish retina regeneration. The Pten gets downregulated upon retinal injury and is absent from the MGPCs, which is essential to trigger Akt-mediated cellular proliferation essential for retina regeneration. We found that the downregulation of Pten in the post-injury retina accelerates MGPCs formation, while its overexpression restricts the regenerative response. We observed that Pten regulates the proliferation of MGPCs not only through Akt pathway but also by Mmp9/Notch signaling. Mmp9-activity is essential to induce the proliferation of MGPCs in the absence of Pten. Lastly, we show that expression of Pten is fine-tuned through Mycb/histone deacetylase1 and Tgf-β signaling. The present study emphasizes on the stringent regulation of Pten and its crucial involvement during the zebrafish retina regeneration.

Detecting genomic mosaicism in "de novo" genetic epilepsy by amplicon-based deep sequencing

AIM

To investigate the occurrence of mosaicism in epilepsy probands and their parents using amplicon-based deep sequencing (ADS).

METHODS

Patients were recruited from the outpatient of Peking University First Hospital. Two hundred and sixty-four probands with pathogenic variants tested by next-generation sequencing (NGS) were enrolled.

RESULTS

Mosaic variants were detected in seventeen disease-associated genes from 20 probands, 5 paternal, and 6 maternal parents. The frequency of mosaicism was 11.74% (31/264). Mosaicism in 11 genes was identified from 20 probands with the mutant allelic fractions (MAFs) of 12.95-38.00% in autosomal dominant genes. Five paternal mosaicisms were identified in genes with a MAF of 6.30-20.99%, and six maternal mosaic individuals with a MAF of 2.07-21.90%. Only four mosaic parents had milder seizure history. The affected sibling had the same phenotype consistent with that of the proband, who inherited the variant of SLC1A2 or STXBP1 from their unaffected mosaic mothers, respectively.

INTERPRETATION

Mosaic phenomenon is not rare in families with epilepsy. Phenotypes of mosaic parents were milder or normal. Mosaicism detection is helpful to identify the mutation origin and it provides a theoretical basis for prenatal diagnosis of family reproduction. ADS is a reliable way of mosaicism detection for clinical application.

Magnitude and relevance of change in health-related quality of life in patients with vascular malformations treated with sirolimus

Introduction

Vascular malformations are rare congenital anomalies of the vascular system, which can involve the capillaries, veins, arteries, lymphatics, or a combination of vessel types. Patients with vascular malformations experience an impaired health-related quality of life (HRQoL) because of their symptoms (e.g., pain, swelling, and bleeding) and psychosocial distress. Sirolimus is an effective drug used in the medical treatment of these patients; however, relatively little is known about the effect of sirolimus on specific changes in the HRQoL domains and its magnitude.

Methods

The magnitude of change (effect size) following intervention is more informative to clinical practitioners than statistically significant but clinically unimportant changes; therefore, this study aimed to examine the magnitude and meaningfulness of change in the HRQoL of children and adults with vascular malformations following sirolimus treatment using low target levels.

Results

In total, 50 patients with vascular malformations (19 children, 31 adults) were included in this study. These patients experienced a lower HRQoL than the general population, with the adults reporting a significantly lower score in almost all domains. A 6-month sirolimus treatment improved the HRQoL in 29 patients, including 77.8% of the children (Pediatric Quality of Life Inventory score [PedsQL]) and 57.7% of the adults (Short Form 36 [SF-36]). The effect sizes of sirolimus for each SF-36/PedsQL domain ranged from 0.19 to 1.02. The clinically relevant moderate magnitude of changes was seen in the domains of the children's reports: "Physical functioning" and "Social functioning" and in the domains of the parent reports: "Social functioning," "School functioning," and "Psychosocial." A high-magnitude change was seen in the domains "Emotional functioning" and "Psychosocial" in the children's reports and "Physical functioning" in the parent reports. In addition, the moderate magnitude of changes was also seen in the adults SF-36: in all domains except for "Role limitations-physical problems," "Role limitations-emotional problems," and "General health perception."

Conclusion

We believe this is the first study showing the magnitude of change in HRQoL after sirolimus treatment in patients with vascular malformations. Before treatment, these patients experienced an impaired HRQoL compared with the general Dutch population. A 6-month sirolimus treatment with low target levels led to moderate-to-high clinically relevant changes in multiple domains, which significantly improved the HRQoL.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT03987152?cond=Vascular+Malformations&cntry=NL&city=Nijmegen&draw=2&rank=1, identifier: NCT03987152.

Cowden Disease: A Review

ABSTRACT

PTEN hamartoma tumor syndrome (PTHS) includes diseases with germline pathogenic variants in the PTEN gene. Cowden syndrome is included in this syndrome . PTEN (phosphatase and tensin homolog) is a tumor suppressor gene located on chromosome 10q22-23; nearly 60%-90% of pathogenic variants are inherited. Cowden syndrome is a rare autosomic dominant condition, affecting approximately 1/200,000 people worldwide. Patients present benign and, malignant neoplasms in multiple organs, mostly breast and thyroid. The skin is the organ affected most consistently by Cowden disease. It is an autosomal dominant condition, characterized clinically by the presence of innumerable verrucous lesions on the skin. Interpretations of histopathologic findings in the cutaneous and mucosal lesions continue to be a matter of debate.

DNA Methyltransferase Inhibitor 5-AZA-DC Regulates TGFβ1-Mediated Alteration of Neuroglial Cell Functions after Oxidative Stress

5-AZA-DC is an efficient methylation inhibitor that inhibits methylation of target DNA. In this study, we explored the effects of 5-AZA-DC on the regulation of TGFβ1 on target genes in neuroglial cell, as well as neuroglial cell functions under oxidative stress. The oxidative stress was constructed by editing CRISPR/Cas9 for knock out Ang-1 and ApoE4 genes. Cells were subjected to TGFβ1OE (or shTGFβ1) transfection and/or 5-AZA-DC intervention. Results showed that under oxidative stress, both TGFβ1OE and shTGFβ1 transfection raised DNMT1, but reduced TGFβ1, PTEN, and TSC2 expressions in neuroglial cells. TGFβ1 directly bind to the promoter of PTEN gene. 5-AZA-DC intervention lowered DNMT1 and raised TGFβ1 expression, as well as promoted the binding between TGFβ1 and promoter of PTEN. TGFβ1OE caused a significant increase in the DNA demethylation level of PTEN promoter, while 5-AZA-DC intervention reduced the DNA demethylation level of PTEN promoter. Under oxidative stress, TGFβ1OE (or shTGFβ1) transfection inhibited neuroglial cell proliferation, migration, and invasion, promoted cell apoptosis. 5-AZA-DC intervention alleviated TGFβ1OE (or shTGFβ1) transfection caused neuroglial cell proliferation, migration, and invasion inhibition, as well as cell apoptosis. To conclude, these results suggest that 5-AZA-DC can be used as a potential drug for epigenetic therapy on oxidative stress damage in neuroglial cells. The findings of this research provide theoretical basis and research ideas for methylation drug intervention and TGFβ1 gene as a possible precise target of glial oxidative stress diagnosis and treatment.

Mosaicism in Tumor Suppressor Gene Syndromes: Prevalence, Diagnostic Strategies, and Transmission Risk

A mosaic state arises when pathogenic variants are acquired in certain cell lineages during postzygotic development, and mosaic individuals may present with a generalized or localized phenotype. Here, we review the current state of knowledge regarding mosaicism for eight common tumor suppressor genes-NF1, NF2, TSC1, TSC2, PTEN, VHL, RB1, and TP53-and their related genetic syndromes/entities. We compare and discuss approaches for comprehensive diagnostic genetic testing, the spectrum of variant allele frequency, and disease severity. We also review affected individuals who have no mutation identified after conventional genetic analysis, as well as genotype-phenotype correlations and transmission risk for each tumor suppressor gene in full heterozygous and mosaic patients. This review provides new insight into similarities as well as marked differences regarding the appreciation of mosaicism in these tumor suppressor syndromes.

When, where and which PIK3CA mutations are pathogenic in congenital disorders

PIK3CA encodes the class I PI3Kα isoform and is frequently mutated in cancer. Activating mutations in PIK3CA also cause a range of congenital disorders featuring asymmetric tissue overgrowth, known as the PIK3CA-related overgrowth spectrum (PROS), with frequent vascular involvement. In PROS, PIK3CA mutations arise postzygotically, during embryonic development, leading to a mosaic body pattern distribution resulting in a variety of phenotypic features. A clear skewed pattern of overgrowth favoring some mesoderm-derived and ectoderm-derived tissues is observed but not understood. Here, we summarize our current knowledge of the determinants of PIK3CA-related pathogenesis in PROS, including intrinsic factors such as cell lineage susceptibility and PIK3CA variant bias, and extrinsic factors, which refers to environmental modifiers. We also include a section on PIK3CA-related vascular malformations given that the vasculature is frequently affected in PROS. Increasing our biological understanding of PIK3CA mutations in PROS will contribute toward unraveling the onset and progression of these conditions and ultimately impact on their treatment. Given that PIK3CA mutations are similar in PROS and cancer, deeper insights into one will also inform about the other.

How we approach the diagnosis of a vascular anomaly

Vascular anomalies represent a diverse group of complex disorders that can cause significant complications, including coagulopathies, pain, and decreased function. The diagnosis of vascular anomalies is often challenging due to heterogeneity of presenting phenotypes and overlapping clinical features with other pediatric conditions. Pediatric hematologists/oncologists (PHO) are uniquely positioned for an essential role in diagnosing, managing, and coordinating the multidisciplinary care required to maximize the quality of life of these patients. Here, we review the diagnostic approach involved in patients with vascular anomalies and utilize cases to highlight the challenges involved, and how PHOs can play a vital part in the care of these patients.

PIK3CA-related overgrowth with an uncommon phenotype: case report

BACKGROUND

Megalencephaly-capillary malformation syndrome is a rare multiple-malformation syndrome secondary to somatic activating mutations in the PI3K-AKT-MTOR pathway. This is included in a heterogeneous group of disorders, now defined "PIK3CA-related overgrowth spectrum".

CASE PRESENTATION

We report a 22-months-old female presenting an uncommon phenotype associated with a genetic mosaicism in the PIK3CA gene, detected on DNA extracted from blood peripheral and tissue biopsy.

CONCLUSIONS

NGS is the preferred method for molecular diagnosis of PROS on affected skin and overgrown tissues as primary samples. The wide phenotypic variability is based on the distribution of mosaicism, in fact the same mutation can cause different PIK3CA related disorders. Continuous understanding of the clinical spectrum and of molecular basis of PROS and their overlap will lead to improve diagnosis, management and new treatment strategies.

The Klippel-Trénaunay Syndrome in 2022: Unravelling Its Genetic and Molecular Profile and Its Link to the Limb Overgrowth Syndromes

The Klippel-Trénaunay syndrome is an unusual syndrome of vascular and dermatologic manifestation in which patients demonstrate hemihypertrophy of the soft tissue and bones of one limb, cutaneous haemangiomas and varicosities in anatomically abnormal positions. Described in 1900 by two French physicians, the etiology remained unclear until recently, when evidence emerged that there was a genetic basis for this sporadic disorder. Genes that encoded pathological angiogenic factors and caused vascular dysmorphogenesis, explaining the molecular bases of this syndrome, were identified. Several angiogenic genes were identified but one gene, the AGGF1 (formerly VG5Q) gene, was seen in mutations involving patients diagnosed with Klippel-Trénaunay syndrome. Furthermore, this syndrome was also noted to have overlapping clinical features linked with the “overgrowth syndromes,” in which genetic mutations along somatic lines were identified. These involved The PI3K enzyme which forms part of the phosphoinositide 3–kinase pathway which is encoded by the PIK3CA-gene. This enzyme mediates embryonic cellular growth in-utero and diseases involved in this pathway are classified as members of the PIK3CA-related overgrowth syndrome. This paper reviews the status of what is now known about the molecular genetics of this unusual, but clinically challenging disorder and its differentiation from similar diseases, linked with the PIK3CA-gene and the related overgrowth syndromes.

mTOR Signaling Components in Tumor Mechanobiology

Mechanistic target of rapamycin (mTOR) is a central signaling hub that integrates networks of nutrient availability, cellular metabolism, and autophagy in eukaryotic cells. mTOR kinase, along with its upstream regulators and downstream substrates, is upregulated in most human malignancies. At the same time, mechanical forces from the tumor microenvironment and mechanotransduction promote cancer cells' proliferation, motility, and invasion. mTOR signaling pathway has been recently found on the crossroads of mechanoresponsive-induced signaling cascades to regulate cell growth, invasion, and metastasis in cancer cells. In this review, we examine the emerging association of mTOR signaling components with certain protein tools of tumor mechanobiology. Thereby, we highlight novel mechanisms of mechanotransduction, which regulate tumor progression and invasion, as well as mechanisms related to the therapeutic efficacy of antitumor drugs.

Carbonic Anhydrase IX Inhibitors as Candidates for Combination Therapy of Solid Tumors

Combination therapy is becoming imperative for the treatment of many cancers, as it provides a higher chance of avoiding drug resistance and tumor recurrence. Among the resistance-conferring factors, the tumor microenvironment plays a major role, and therefore, represents a viable target for adjuvant therapeutic agents. Thus, hypoxia and extracellular acidosis are known to select for the most aggressive and resilient phenotypes and build poorly responsive regions of the tumor mass. Carbonic anhydrase (CA, EC 4.2.1.1) IX isoform is a surficial zinc metalloenzyme that is proven to play a central role in regulating intra and extracellular pH, as well as modulating invasion and metastasis processes. With its strong association and distribution in various tumor tissues and well-known druggability, this protein holds great promise as a target to pharmacologically interfere with the tumor microenvironment by using drug combination regimens. In the present review, we summarized recent publications revealing the potential of CA IX inhibitors to intensify cancer chemotherapy and overcome drug resistance in preclinical settings.

Lateralized and Segmental Overgrowth in Children

Congenital disorders of lateralized or segmental overgrowth (LO) are heterogeneous conditions with increased tissue growth in a body region. LO can affect every region, be localized or extensive, involve one or several embryonic tissues, showing variable severity, from mild forms with minor body asymmetry to severe ones with progressive tissue growth and related relevant complications. Recently, next-generation sequencing approaches have increased the knowledge on the molecular defects in LO, allowing classifying them based on the deranged cellular signaling pathway. LO is caused by either genetic or epigenetic somatic anomalies affecting cell proliferation. Most LOs are classifiable in the Beckwith-Wiedemann spectrum (BWSp), PI3KCA/AKT-related overgrowth spectrum (PROS/AROS), mosaic RASopathies, PTEN Hamartoma Tumor Syndrome, mosaic activating variants in angiogenesis pathways, and isolated LO (ILO). These disorders overlap over common phenotypes, making their appraisal and distinction challenging. The latter is crucial, as specific management strategies are key: some LO is associated with increased cancer risk making imperative tumor screening since childhood. Interestingly, some LO shares molecular mechanisms with cancer: recent advances in tumor biological pathway druggability and growth downregulation offer new avenues for the treatment of the most severe and complicated LO.

Lipomatous Infiltration in Tuberous Sclerosis Complex - A Case Series and Literature Review

Diffuse Lipomatosis is a dermatological lesion consisting of a poorly circumscribed, infiltrative overgrowth of mature adipose tissue that usually affects the trunk and the extremities. The lesions in the Tuberous Sclerosis Complex (TSC) are usually hamartomatous in nature, but lesions arising from adipocytes are rare. There are only three previous reports of association of TSC with diffuse lipomatosis. Herein we present a case series of diffuse lipomatosis in three subjects with TSC and proceed to review the literature for any other reported cases. On the basis of the three index cases and identification of three more cases in the literature, we believe that there is an association of diffuse lipomatosis with TSC that has not been appreciated until now. We believe that this association in some selected cases will serve to improve diagnosis, surveillance, and management..

Targeted Sequencing Revealed Distinct Mutational Profiles of Ocular and Extraocular Sebaceous Carcinomas

The biological behavior of sebaceous carcinoma (SeC) is relatively indolent; however, local invasion or distant metastasis is sometimes reported. Nevertheless, a lack of understanding of the genetic background of SeC makes it difficult to apply effective systemic therapy. This study was designed to investigate major genetic alterations in SeCs in Korean patients. A total of 29 samples, including 20 ocular SeCs (SeC-Os) and 9 extraocular SeCs (SeC-EOs), were examined. Targeted next-generation sequencing tests including 171 cancer-related genes were performed. TP53 and PIK3CA genes were frequently mutated in both SeC-Os and SeC-EOs with slight predominance in SeC-Os, whereas the NOTCH1 gene was more commonly mutated in SeC-EOs. In clinical correlation, mutations in RUNX1 and ATM were associated with development of distant metastases, and alterations in MSH6 and BRCA1 were associated with inferior progression-free survival (all p < 0.05). In conclusion, our study revealed distinct genetic alterations between SeC-Os and SeC-EOs and some important prognostic molecular markers. Mutations in potentially actionable genes, including EGFR, ERBB2, and mismatch repair genes, were noted, suggesting consideration of a clinical trial in intractable cases.

Congenital vascular lesions, could MAPK and PI3K inhibitors pave the way to new therapies?

PURPOSE OF REVIEW

Superficial vascular anomalies are a heterogeneous group of malformative and tumoral lesions, developed from various types of abnormal lymphatic and/or blood vessels. They are mostly benign but their clinical evolution can lead to dramatic cosmetic concern, functional impairment and even life-threatening conditions. Until recently, treatments relied on invasive procedures such as embotherapy/sclerotherapy and/or surgery. Recent molecular findings pave the way of new medical therapies.

RECENT FINDINGS

Two main signaling pathways PI3K-AKT-mTOR and RAS-MAPK-ERK are now identified to encounter for the causative pathogenic genetic variants of most vascular anomalies. Involved genes are also responsible for several common neoplasms for which targeted therapies are already available or under development. Repurposing treatment strategy is considered for vascular anomalies treatment with promising results.

SUMMARY

The mTOR inhibitor sirolimus is the most used targeted therapy so far but new molecules are tested currently.

A review of mechanisms of disease across PIK3CA-related disorders with vascular manifestations

BACKGROUND

PIK3CA-related disorders include vascular malformations and overgrowth of various tissues that are caused by postzygotic, somatic variants in the gene encoding phosphatidylinositol-3-kinase (PI3K) catalytic subunit alpha. These mutations result in activation of the PI3K/AKT/mTOR signaling pathway. The goals of this review are to provide education on the underlying mechanism of disease for this group of rare conditions and to summarize recent advancements in the understanding of, as well as current and emerging treatment options for PIK3CA-related disorders.

MAIN BODY

PIK3CA-related disorders include PIK3CA-related overgrowth spectrum (PROS), PIK3CA-related vascular malformations, and PIK3CA-related nonvascular lesions. Somatic activating mutations (predominantly in hotspots in the helical and kinase domains of PIK3CA, but also in other domains), lead to hyperactivation of the PI3K signaling pathway, which results in abnormal tissue growth. Diagnosis is complicated by the variability and overlap in phenotypes associated with PIK3CA-related disorders and should be performed by clinicians with the required expertise along with coordinated care from a multidisciplinary team. Although tissue mosaicism presents challenges for confirmation of PIK3CA mutations, next-generation sequencing and tissue selection have improved detection. Clinical improvement, radiological response, and patient-reported outcomes are typically used to assess treatment response in clinical studies of patients with PIK3CA-related disorders, but objective assessment of treatment response is difficult using imaging (due to the heterogeneous nature of these disorders, superimposed upon patient growth and development). Despite their limitations, patient-reported outcome tools may be best suited to gauge patient improvement. New therapeutic options are needed to provide an alternative or supplement to standard approaches such as surgery and sclerotherapy. Currently, there are no systemic agents that have regulatory approval for these disorders, but the mTOR inhibitor sirolimus has been used for several years in clinical trials and off label to address symptoms. There are also other agents under investigation for PIK3CA-related disorders that act as inhibitors to target different components of the PI3K signaling pathway including AKT (miransertib) and PI3K alpha (alpelisib).

CONCLUSION

Management of patients with PIK3CA-related disorders requires a multidisciplinary approach. Further results from ongoing clinical studies of agents targeting the PI3K pathway are highly anticipated.

Dermatologic findings in individuals with genetically confirmed Proteus syndrome

BACKGROUND/OBJECTIVE

Proteus syndrome, caused by a mosaic activating AKT1 variant, typically presents in toddlers with progressive, asymmetric overgrowth of the skin and bones. We aimed to define the spectrum of dermatologic disease in individuals with genetically confirmed Proteus syndrome.

METHODS

We conducted a retrospective review of records from dermatologic examinations of individuals evaluated at the NIH with a molecular diagnosis of Proteus syndrome. The types, prevalence, and localization of dermatologic findings were assessed.

RESULTS

Fifty-one individuals (29 males, 22 females, mean age: 9 years) with clinical features of Proteus syndrome had the mosaic c.49G>A, p.Glu17Lys AKT1 variant. Fifty (98%) had at least one cutaneous feature constituting current clinical diagnostic criteria, including vascular malformations in 42 (82%), epidermal nevus in 41 (80%), volar cerebriform connective tissue nevi in 34 (67%), and adipose dysregulation in 30 (59%). Forty-nine (96%) had at least one dermatologic finding not included within the diagnostic criteria, including confluent volar skin-colored to hypopigmented papules or nodules (n = 33, 65%), papules or nodules on the digits or face (n = 27, 53%), and nonlinear epidermal nevi (n = 15, 29%). Other frequently observed features include nail changes (n = 28, 55%), hyperpigmented macules (n = 27, 53%), patchy dermal hypoplasia (n = 18, 35%), gingival/oral mucosal overgrowth (n = 17, 33%), hypopigmented macules (n = 16, 31%), dental enamel changes (n = 9, 18%), acrochordons (n = 6, 12%), and lingual overgrowth (n = 4, 8%).

CONCLUSIONS

The range of mucocutaneous features occurring in Proteus syndrome is broader than previously considered. These observations may assist in earlier diagnosis and management and provide novel insights regarding the pathogenesis of the condition.

Tsc Gene Locus Disruption and Differences in Renal Epithelial Extracellular Vesicles

In tuberous sclerosis complex (TSC), Tsc2 mutations are associated with more severe disease manifestations than Tsc1 mutations and the role of extracellular vesicles (EVs) in this context is not yet studied. We report a comparative analysis of EVs derived from isogenic renal cells except for Tsc1 or Tsc2 gene status and hypothesized that in spite of having similar physical characteristics, EVs modulate signaling pathways differently, thus leading to TSC heterogenicity. We used mouse inner medullary collecting duct (mIMCD3) cells with the Tsc1 (T1G cells) or Tsc2 (T2J cells) gene disrupted by CRISPR/CAS9. EVs were isolated from the cell culture media by size-exclusion column chromatography followed by detailed physical and chemical characterization. Physical characterization of EVs was accessed by tunable resistive pulse sensing and dynamic light scattering, revealing similar average sizes and zeta potentials (at pH 7.4) for EVs from mIMCD3 (123.5 ± 5.7 nm and −16.3 ± 2.1 mV), T1G cells (131.5 ± 8.3 nm and −19.8 ± 2.7 mV), and T2J cells (127.3 ± 4.9 nm and −20.2 ± 2.1 mV). EVs derived from parental mIMCD3 cells and both mutated cell lines were heterogeneous (>90% of EVs < 150 nm) in nature. Immunoblotting detected cilial Hedgehog signaling protein Arl13b; intercellular proteins TSG101 and Alix; and transmembrane proteins CD63, CD9, and CD81. Compared to Tsc2 deletion, Tsc1 deletion cells had reduced EV production and release rates. EVs from Tsc1 mutant cells altered mTORC1, autophagy, and β-catenin pathways differently than EVs from Tsc2-mutated cells. Quantitative PCR analysis revealed the down regulation of miR-212a-3p and miR-99a-5p in EVs from Tsc2-mutated cells compared to EVs from Tsc1-mutant cells. Thus, EV-derived miR-212-3p and mIR-99a-5p axes may represent therapeutic targets or biomarkers for TSC disease.

Phenotype and Surgical Treatment in a Case of Proteus Syndrome With Craniofacial and Oral Findings

BACKGROUND/AIM

Proteus syndrome is a sporadic disease that is particularly noticeable due to the disproportional growth of body segments. The disease is a genetic mosaic. The mutations can arise from any of the germ layers, an explanation of the very variable phenotype. The aim of this report is to communicate the diagnosis and management of an unusual case of Proteus Syndrome with special attention to oral and craniofacial findings.

CASE REPORT

A 15-year-old patient was referred for surgical treatment of pronounced skull malformations and correction of oral mucosal hyperplasia. Treatment caused significant improvement in facial appearance and oral soft tissue conditions.

CONCLUSION

Surgical measures adapted to the local findings and symptoms can often relieve severe disfigurement of the patient.

Patients with Congenital Low-Flow Vascular Malformation Treated with Low Dose Sirolimus

INTRODUCTION

Patients with congenital vascular malformations often suffer from an impaired quality of life (QoL) because of pain and functional disabilities. Previous studies have shown that the mTOR inhibitor sirolimus can reduce complaints and improve QoL in some patients. High target levels of sirolimus of 10-15 ng/ml were well tolerated; however, in a relative high percentage of patients sirolimus caused serious adverse events (AEs).

METHODS

A case series of 12 patients with therapy-resistant low-flow vascular malformations was treated with sirolimus, using low target levels of 4-10 ng/ml. Efficacy of sirolimus was evaluated in regard to pain symptoms using the visual analogue scale/numeric rating scale and patients reported QoL. To rule out a placebo effect of sirolimus, sirolimus was stopped after a certain time point and reintroduced as soon as complaints returned. Adverse events were closely monitored and graded using the Common Terminology Criteria for Adverse Events (CTCAE) grading.

RESULTS

An improvement in symptoms was seen in 92% (n = 11/12) of patients. In nine patients pain complaints returned. Seven out of nine of them (78%) again experienced a reduction of symptoms after restarting sirolimus treatment. Despite low target levels, these response rates are comparable to those found in the literature using higher target levels of sirolimus. However, significantly less serious AEs were observed with low dose sirolimus, suggesting low dose sirolimus might be safer. Unfortunately, young adolescent female patients developed serious menstrual disturbances during treatment with low dose sirolimus. We describe this adverse event for the first time in patients with congenital vascular malformations and this might be specifically related to low dose sirolimus.

CONCLUSIONS

Low dose sirolimus showed a high efficacy in patients with therapy-resistant and low-flow malformation, with a lower incidence of serious adverse events. At the same time a new adverse event, namely menstrual cycle disturbance, was observed in young adolescents, indicating the need for caution when sirolimus is given. This is extremely relevant to patients with low-flow vascular malformation, who are likely to require lifelong treatment for their condition.

PTEN somatic mutations contribute to spectrum of cerebral overgrowth

Phosphatase and tensin homolog (PTEN) regulates cell growth and survival through inhibition of the mammalian target of rapamycin (MTOR) signaling pathway. Germline genetic variation of PTEN is associated with autism, macrocephaly, and PTEN hamartoma tumor syndromes (PHTS). The effect of developmental PTEN somatic mutations on nervous system phenotypes is not well understood, although brain somatic mosaicism of MTOR pathway genes is an emerging cause of cortical dysplasia and epilepsy in the pediatric population. Here we report two somatic variants of PTEN affecting a single patient presenting with intractable epilepsy and hemimegalencephaly that varied in clinical severity throughout the left cerebral hemisphere. High-throughput sequencing analysis of affected brain tissue identified two somatic variants in PTEN. The first variant was present in multiple cell lineages throughout the entire hemisphere and associated with mild cerebral overgrowth. The second variant was restricted to posterior brain regions and affected the opposite PTEN allele, resulting in a segmental region of more severe malformation, and the only neurons in which it was found by single-nuclei RNA-seq had a unique disease-related expression profile. This study reveals brain mosaicism of PTEN as a disease mechanism of hemimegalencephaly and furthermore demonstrates the varying effects of single- or bi-allelic disruption of PTEN on cortical phenotypes.

Cross talk between autophagy and oncogenic signaling pathways and implications for cancer therapy

Autophagy is a highly conserved metabolic process involved in the degradation of intracellular components including proteins and organelles. Consequently, it plays a critical role in recycling metabolic energy for the maintenance of cellular homeostasis in response to various stressors. In cancer, autophagy either suppresses or promotes cancer progression depending on the stage and cancer type. Epithelial-mesenchymal transition (EMT) and cancer metastasis are directly mediated by oncogenic signal proteins including SNAI1, SLUG, ZEB1/2, and NOTCH1, which are functionally correlated with autophagy. In this report, we discuss the crosstalk between oncogenic signaling pathways and autophagy followed by possible strategies for cancer treatment via regulation of autophagy. Although autophagy affects EMT and cancer metastasis, the overall signaling pathways connecting cancer progression and autophagy are still illusive. In general, autophagy plays a critical role in cancer cell survival by providing a minimum level of energy via self-digestion. Thus, cancer cells face nutrient limitations and challenges under stress during EMT and metastasis. Conversely, autophagy acts as a potential cancer suppressor by degrading oncogenic proteins, which are essential for cancer progression, and by removing damaged components such as mitochondria to enhance genomic stability. Therefore, autophagy activators or inhibitors represent possible cancer therapeutics. We further discuss the regulation of autophagy-dependent degradation of oncogenic proteins and its functional correlation with oncogenic signaling pathways, with potential applications in cancer therapy.

Pathogenic postzygotic mosaicism in the tyrosine receptor kinase pathway: potential unidentified human disease hidden away in a few cells

Mutations occurring during embryonic development affect only a subset of cells resulting in two or more distinct cell populations that are present at different levels, also known as postzygotic mosaicism (PZM). Although PZM is a common biological phenomenon, it is often overlooked as a source of disease due to the challenges associated with its detection and characterization, especially for very low-frequency variants. Moreover, PZM can cause a different phenotype compared to constitutional mutations. Especially, lethal mutations in receptor tyrosine kinase (RTK) pathway genes, which exist only in a mosaic state, can have completely new clinical manifestations and can look very different from the associated monogenic disorder. However, some key questions are still not addressed, such as the level of mosaicism resulting in a pathogenic phenotype and how the clinical outcome changes with the development and age. Addressing these questions is not trivial as we require methods with the sensitivity to capture some of these variants hidden away in very few cells. Recent ultra-accurate deep-sequencing approaches can now identify these low-level mosaics and will be central to understand systemic and local effects of mosaicism in the RTK pathway. The main focus of this review is to highlight the importance of low-level mosaics and the need to include their detection in studies of genomic variation associated with disease.

Upregulation of miR-137 Expression Suppresses Tumor Growth and Progression via Interacting with DNMT3a Through Inhibiting the PTEN/Akt Signaling in HCC

Background

Downregulation of miR-137 regulates tumor growth in hepatocellular carcinoma (HCC). Yet, the underlying molecular mechanisms stay unclear.

Materials and Methods

miR-137 and DNA methyltransferase 3a (DNMT3a) expression levels were detected by Western blot, immunohistochemistry and qRT-PCR assays. Luciferase reporter and Western blot assays were also carried out to explore the correlation of miR-137 and DNMT3a. Flow cytometry assay, MTT analysis, transwell and wound healing assay were used to evaluate cell apoptosis, proliferation, as well as invasive and migratory abilities. Western blot was used to examine the caspase-3, cleaved caspase-3, PCNA, MMP-2, and MMP-7 protein levels, as well as PTEN/Akt signaling alternations. Methylation-specific PCR was applied to detect the PTEN promoter methylation status. Xenograft tumor assay, Western blot and immunohistochemistry analyses were taken to confirm the miR-137 regulation in vivo.

Results

Downregulation of miR-137, upregulation of DNMT3a, as well as an inverse correlation between them were observed in HCC clinical samples and cells. Moreover, miR-137 targeted directly and inhibited DNMT3a in HCC cells, which further retarded cell proliferative, migratory and invasive capabilities, while promoted apoptotic ones. Additionally, miR-137 overexpression inactivated the PTEN/Akt pathway in HCC cell by decreasing DNMT3a expression. Furthermore, miR-137 overexpression inhibited tumor growth in vivo in HCC via interacting with DNMT3a through inhibiting the PTEN/Akt cascades.

Conclusion

Our findings suggested that miR-137 inhibited HCC tumor growth and progression via interacting with DNMT3a and suppressing the PTEN/Akt signaling in vitro and in vivo.

Surgical management for isolated macrodactyly in an adult PIK3CA mutant

Isolated macrodactyly in adults caused by mosaic pattern PIK3CA mutation can result in significant functional impairment and psychological burden. Due to the rarity of this condition there are no clear treatment guidelines, and those few available are focused on paediatric cases. Reports on surgical management of isolated macrodactyly in adults are lacking. We present here the surgical management through partial amputation of enlarged rays of the right hand in an individual affected by low-grade mosaic PIK3CA mutation.

Update on extracranial arteriovenous malformations: A staged multidisciplinary approach

Arteriovenous malformations (AVMs) are vascular lesions that are thought to arise from congenital errors during development of vessels resulting in abnormal connections between arteries and veins. Though most AVMs develop in the brain or spinal cord, they can occur anywhere in the body. These extracranial or peripheral AVMs have a predilection for the head, neck, and limbs. Since these malformations infiltrate normal soft tissue, management requires selective treatment with preservation of normal surrounding architecture. Therefore, they are best addressed through a staged multimodal and multidisciplinary approach, using a combination of different laser, interstitial, intravascular and surgical techniques to specifically target anomalous vessels. The goal of treatment is overall disease improvement and symptom control with interventions that do not result in outcomes worse than the disease itself. Recently, the discovery of somatic and germline mutations in peripheral AVMs have contributed to a better understanding of the pathophysiology, resulting in promising new pharmacologic treatments. Recent evidence suggests that adjuvant medical therapy can enhance and sustain interventional and/or surgical outcomes. Herein we describe how a new understanding of the etiology and physiology of extracranial AVM provides guidance to current treatment approaches.

Overgrowth syndromes and new therapies

Overgrowth syndromes represent a diverse group of disorders with overlapping features. Interdisciplinary management by a team of experts in vascular anomalies is crucial for establishing the correct diagnosis and optimizing outcomes for these patients. Unique management considerations include increased risk for thrombosis and in some cases, cancer. In recent years, research has demonstrated that these disorders are primarily caused by somatic mutations in growth pathways, particularly the PI3K-mTOR pathway. This improved understanding had led to promising new therapies for this group of patients.

Detailed analysis of phenotypes and genotypes in megalencephaly-capillary malformation-polymicrogyria syndrome caused by somatic mosaicism of PIK3CA mutations

Background

Megalencephaly-capillary malformation-polymicrogyria syndrome (MCAP) belongs to a group of conditions called the PIK3CA-related overgrowth spectrum (PROS). The varying phenotypes and low frequencies of each somatic mosaic variant make confirmative diagnosis difficult. We present 12 patients who were diagnosed clinically and genetically with MCAP. Genomic DNA was extracted mainly from the skin of affected lesions, also from peripheral blood leukocytes and buccal epithelial cells, and target panel sequencing using high-depth next-generation sequencing technology was performed.

Results

Macrocephaly was present in 11/12 patients (92%). All patients had normal body asymmetry. Cutaneous vascular malformation was found in 10/12 patients (83%). Megalencephaly or hemimegalencephaly was noted in all 11 patients who underwent brain magnetic resonance imaging. Arnold–Chiari type I malformation was also seen in 10 patients. Every patient was identified as having pathogenic or likely pathogenic variants of the PIK3CA gene. The variant allele frequency (VAF) ranged from 6.3 to 35.3%, however, there was no direct correlation between VAF and the severity of associated anomalies. c.2740G > A (p.Gly914Arg) was most commonly found, in four patients (33%). No malignancies developed during follow-up periods.

Conclusions

This is the first and largest cohort of molecularly diagnosed patients with MCAP in Korea. Targeted therapy with a PI3K-specific inhibitor, alpelisib, has shown successful outcomes in patients with PROS in a pilot clinical study, so early diagnosis for genetic counseling and timely introduction of emerging treatments might be achieved in the future through optimal genetic testing.

Genitourinary involvement in pediatric patients with Klippel-Trenaunay Syndrome

BACKGROUND

Klippel-Trenaunay Syndrome (KTS) is a genetic vascular malformation disorder which induces a variety of phenotypic expression in patients which differ in terms of severity/location. While previous studies have documented genitourinary (GU) complications in adult KTS patients, documentation of the scope and incidence of GU involvement in the pediatric population with imaging findings is currently limited. This study represents the largest KTS genitourinary review to date.

OBJECTIVE

To assess the incidence, scope, clinical findings and imaging characteristics of GU pathology in pediatric KTS patients.

MATERIALS/METHODS

Using a retrospective data analysis design, the charts and imaging studies of pediatric KTS patients were reviewed. All patients received care at a specialized vascular clinic within a multicenter tertiary care system. Variables studied included age, age at KTS diagnosis, gender, urologic involvement, and age of urologic complication.

RESULTS

58 patients were identified. 33 were male and 25 were female. 10 patients had GU findings. Three of these patients had multifocal GU involvement (greater than 1 finding). Urologic manifestations were diverse with 9 distinct diagnoses involving 6 unique organs. Renal, vesical and scrotal pathologies were most common. Hematuria was the most common presenting symptom in 30% (3/10). Previously unreported findings (labial swelling, renal lymphatic cysts) were identified. The average age of KTS diagnosis was 4.9 years. The average age of documented GU complication and involvement was 7.6 years.

CONCLUSION

Significant GU complications due to KTS can occur in the pediatric population. Early clinical and imaging characterization of these conditions is important for management, family education and early intervention strategies.

Parental somatic mosaicism for CNV deletions - A need for more sensitive and precise detection methods in clinical diagnostics settings

To further assess the scale and level of parental somatic mosaicism, we queried the CMA database at Baylor Genetics. We selected 50 unrelated families where clinically relevant apparent de novo CNV-deletions were found in the affected probands. Parental blood samples screening using deletion junction-specific PCR revealed four parents with somatic mosaicism. Droplet digital PCR (ddPCR), qPCR, and amplicon-based next-generation sequencing (NGS) were applied to validate these findings. Using ddPCR levels of mosaicism ranged from undetectable to 18.5%. Amplicon-based NGS and qPCR for the father with undetectable mosaicism was able to detect mosaicism at 0.39%. In one mother, ddPCR analysis revealed 15.6%, 10.6%, 8.2%, and undetectable levels of mosaicism in her blood, buccal cells, saliva, and urine samples, respectively. Our data suggest that more sensitive and precise methods, e.g. CNV junction-specific LR-PCR, ddPCR, or qPCR may allow for a more refined assessment of the potential disease recurrence risk for an identified variant.

Prevalence and Impact of Underlying Diagnosis and Comorbidities on Chiari 1 Malformation

BACKGROUND

Chiari malformation type 1 affects approximately one in 1,000 people symptomatically, although one in 100 meet radiological criteria, making it a common neurological disorder. The diagnosis of underlying conditions has become more sophisticated, and new radiological markers of disease have been described. We sought to determine the prevalence and impact of additional comorbidities and underlying diagnoses in patients with Chiari malformation type 1 on symptomatology and surgical treatment.

METHODS

A retrospective review of 612 pediatric patients with a Chiari malformation type 1 diagnosis and imaging data evaluated between 2008 and 2018 was performed. Because of extensive clinical heterogeneity, patients were separated into four categories based on their primary comorbidities (nonsyndromic, central nervous system, skeletal, and multiple congenital anomalies) to identify associations with age of onset, radiographic measurements, syringomyelia, and surgical treatment.

RESULTS

The largest group had nonsyndromic Chiari malformation type 1 (70%) and the latest age at diagnosis of any group. In the syndromic group, 6% were diagnosed with a known genetic abnormality, with overgrowth syndromes being the most common. Patients with multiple congenital anomalies had the earliest Chiari malformation type 1 onset, the most severe tonsillar ectopia and obex position, and were overrepresented among surgical cases. Although there were no statistically significant differences between groups and rates of syrinx, we observed differences in individual diagnoses.

CONCLUSION

The underlying diagnoses and presence of comorbidities in patients with Chiari malformation type 1 impacts rates of syringomyelia and surgery. Although most Chiari malformation type 1 cases are nonsyndromic, clinical evaluation of growth parameters, scoliosis, and joint hypermobility should be routine for all patients as they are useful to determine syringomyelia risk and may impact treatment.